REGIONAL OVERVIEW

Biological diversity or 'biodiversity' means the variety of plant and animal
life at the ecosystem, community or species level, and even at the genetic level.
Biodiversity is most commonly measured and reported at species level with characteristics
such as species richness (number of species), species diversity (types of species),
and endemism (uniqueness of species to a certain area) being the most useful
elements for comparison.

Only a fraction of the species inhabiting the earth have been identified and
studied to date and the roles they play in influencing the environment are still
often poorly understood. Studies have tended to concentrate on higher plants
and mammals and such species have also been the focus of most conservation efforts.
This can give a misleading impression of the importance of 'lower organisms'
such as bacteria, insects, and fungi which play vital ecological roles-for example,
in nutrient cycling, and regulation of water, soil and air quality. Lack of
understanding of the role of such organisms can lead to their being 'sidelined'
when conservation efforts or commercial utilization are being considered. It
is worth noting that around 1 million of the 1.75 million species described
so far are insects and myriapods, and that the total number of such species
is estimated to be around 8 million. In other words, only one-eighth of insect
and myriapod species have been identified and recorded to date. It is also estimated
that there are 1.5 million species of fungi, of which 72 000 have been described,
and 1 million species of bacteria, of which a mere 4 000 have been described
(WCMC 2000).

Africa has rich and varied biological resources forming
the region's natural wealth on which its social and economic systems are based.
These resources also have global importance, for the world's climate and for
the development of agriculture or industrial activities such as pharmaceutics,
tourism or construction, to name but a few of the most important areas.

Africa is also a continent of extremes, both in terms of physical features
and climatic conditions, and therefore in terms of the life it supports. The
humid tropical forests of equatorial Africa are among the most productive ecosystems
in the world with Net Primary Productivity (NPP)-the net flux of carbon from
the atmosphere into green plants-greater than 800 gCarbon/m2/yr). They also
support an estimated 1.5 million species. By contrast, Africa's arid areas are
among the harshest environments in the world. The Sahara and Namib deserts and
the Sahel, for example, have NPP of just 100 gCarbon/m2/yr (WCMC 2000). But
even under these conditions many plant and animal species manage to thrive.

The designation of some areas as 'biodiversity hotspots' is a useful concept
developed in recent years as a means of prioritizing habitats for conservation
Myers 1990). Hotspots are areas where species diversity and endemism are particularly
high and where there is an extraordinary threat of loss of species or habitat.
There are 25 internationally recognized hotspots, six of them are in Africa
(Mittermeier, Myers, Gil & Mittermeier 2000). These are shown in Figure
2b.1 and are described below:

The Mediterranean Basin Forests constitute just 1.5 per cent of the
world's forests, yet are home to 25 000 plant species and 14 endemic genera
(Quézel, Médail, Loisel, & Barbero 1999).

The Western Indian Ocean Islands have extremely high levels of endemism
due to their isolation. This is especially true for Madagascar which has the
highest number of endemic species in Africa (including 700 endemic vertebrate
species), and ranks 6th in the world (UNEP 1999).

The Cape Floristic Region, in South Africa, is the smallest and richest
of the world's floral kingdoms with 68 per cent of the 8 700 plant species
endemic to the region (Low & Rebelo 1996).

The Succulent Karoo, shared between South Africa and Namibia, is
the richest desert in the world-40 per cent of its 4 849 species are endemic
(Low & Rebelo 1996).

The Guinean Forest hotspot is a strip of fragmented forest running
parallel to the coast of Western Africa through 11 countries from Guinea to
Cameroon. It has the highest mammalian diversity of all of the world's 25
hotspots (551 species out of the 1 150 mammalian species on the African continent)
and contains 2 250 plant species, 90 bird species, 45 mammal species and 46
reptile species found nowhere else (Conservation International 2002, Mittermeier
and others 2000).

The Eastern Arc Mountain Forests of Eastern Africa are 30 million
years old and are thought to have evolved in isolation for at least 10 million
years. As a result, more than 25 per cent of the plant species are endemic
(Lovett 1998).

Africa also has several areas where both species richness and degree of threat
are high but endemism is lower. These 'potential hotspots' include the highlands
of Ethiopia; the forests of the Albertine Rift in eastern Congo, Rwanda, Burundi
and adjacent parts of Uganda and Kenya; the western escarpment of Angola; and
the Miombo Woodlands of interior Southern Africa (Mittermeier and others 2000).

Africa also has a range of aquatic habitats with very high levels of biodiversity.
Marine ecosystems tend to be more diverse than terrestrial ones and reach even
higher levels of diversity in warmer tropical waters than in cooler seas. The
coasts of many African countries have rich ecosystems such as coral reefs, seagrass
meadows, mangrove forests, estuaries and floodplain swamps (Martens 1995). Rivers,
lakes (freshwater and soda) and riverine edge swamps, valley swamps, seasonal
floodplains, ponds and high altitude peatforming wetlands all contribute to
a wide variety of aquatic ecosystems in Africa that support an extensive range
of resident as well as migratory species (Harper & Mavuti 1996).

The national and sub-regional boundaries that characterize present day Africa
are the result of geographical and human activities often determined by political
or economic factors, they therefore seldom reflect the boundaries of ecological
systems. This difference between political and ecological units is significant-when
the boundaries of ecosystems extend beyond territorial boundaries, the protection
of the natural resources within those ecosystems requires management strategies
that are coordinated jointly between nations or sub-regions (Westing 1993).
The disparities between political and ecological boundaries also imply some
overlap in discussion of biological systems in the sub-regions referred to in
this report. For example, Tanzania forms part of the Southern African sub-region
but shares major ecological systems with Kenya and Uganda. It is therefore discussed
in both the Southern Africa and Eastern Africa analyses.